1. Field of the Invention
The present invention relates in general to a power transmission system of a vehicle, and more particularly to a power transmission method and a power transmission device for intermittently transmit the rotational force of an engine output shaft to an input shaft of a transmission gear box.
2. Description of the Prior Art
A conventional vehicle, such as an automobile driven by the rotational force of an internal combustion engine or a hydraulic-powered machine driven by the hydraulic pump delivery generated by the rotational force of a drive motor, is necessarily provided with a power transmission device, such as a clutch device, in order to intermittently transmit the rotational force of the output shaft of the engine or of the motor to an input shaft of a transmission gear box of the vehicle while controlling the rotational speed of the shaft.
There have been proposed a variety of clutch devices which are generally classified in accordance with their manipulation patterns and their constructions. As known to those skilled in the art, the known clutch devices except for the automatic clutches are manually controlled.
In order to achieve such a manual control for the manual clutch device, the clutch device should be often handled to intermit the power transmission as occasion demands irrespective of the number of revolutions of the engine output shaft. In this regard, the known manual clutch device has a disadvantage in that every handling for the clutch device causes the engine to be imparted with an undesirable starting load.
On the other hand, the known automatic clutch devices achieve the clutching operation using a torque converter which is a kind of power transmission device of the indirect type using the hydraulic clutching power, thus causing a disadvantage in that a large amount of fuel should be required to achieve the clutching operation.